This might sound a bit stupid but a friend of mine had this idea and I thought: why not ask the Ubuntu forum.

Is it possible to let a Linux kernel run when you boot into Windows (after choosing it in the GRUB loader).
When Windows shuts down the Linux kernel encrypts Windows as it is and when you boot back into windows Linux will decrypt windows. Like hibernating or the Suspend function in Vmware. But he thinks that this could be faster. And when you hibernate to often Windows will get slower and slower until it's rebooted (Don't know if other people have that same problem).

That was the question.
I sure hope it's possible
And thanks in advance.